Abstract: Under suitable experimental conditions, some twisted graphene multilayers and transition-metal dichalcogenides become Chern insulators, exhibiting the anomalous quantum Hall effect and orbital magnetization due to spontaneous valley polarization. We study (theoretically) the interaction of a Chern insulator with circularly polarized light, originating from the optical Stark energy shift. The interaction energy contains an antisymmetric term that couples the helicity of incident light and the Berry curvature of the electronic system. Taking advantage of this interaction, we propose an experimental protocol for switching the sign of the Chern number, representing topological memory, by circularly polarized light [1]. This framework is also applicable to the kagome material KV3Sb5, where the time-reversal symmetry is spontaneously broken by three coexisting charge-density waves.
Using the same formalism, we also show that circular stirring of an optical lattice can induce a controlled direct current of bosonic atoms loaded into the lattice [2], similarly to the circular photogalvanic effect in solid-state physics. This effect can be used to transport neutral bosonic atoms in an optical lattice over a given distance in a specified direction.
[1] Sergey S. Pershoguba and Victor M. Yakovenko, “Optical control of topological memory based on orbital magnetization”, Phys. Rev. B 105, 064423 (2022)
[2] Sergey S. Pershoguba and Victor M. Yakovenko, “Direct current in a stirred optical lattice”, arXiv:2205.15981
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